Injectable PrEP Frequently Asked Questions – Clinical
The information in this FAQ provides general guidance and reflects what is currently understood about Cabotegravir-LA (Apretude) based on data from HPTN 083 and post-marketing experience. Readers should consult the package insert and/or obtain expert guidance in the management of individual patients.
- Time to protection is not known with certainty for any form of PrEP.
- The available evidence based on animal models suggests 95% of people will achieve protective blood levels of CAB-LA 7 days after their first injection. Fifty percent of people will achieve protective blood levels 1 day after the first injection.
For reference, the target blood level is 0.664 μg/mL, which is four times the protein-adjusted (PA)-IC90. The IC90 of a drug is the drug concentration that will inhibit replication of 90% of HIV virus. The plasma concentrations associated with protection were identified in preclinical animal and phase 2 trials. In animal studies, >1X PA IC90 was 97% protective for nonhuman primates, and >3X PA IC90 was 100% protective. In phase 2 trials, 600mg of CAB LA dosed every 8 weeks resulted in plasma concentrations >4X PA IC90 for the majority of the population studied. This dose was moved forward for the HPTN studies. Four times that level is thought to be a conservative enhancement of that level of viral inhibition.
Injection site reactions (ISR) including pain, induration and swelling are the most common side effect and are more likely with the first few injections. In HPTN 083, 75% of participants in the CAB-LA arm who received at least one injection reported injection site pain. Clinicians should counsel patients around prevention and management of ISRs. Helpful strategies may include over-the-counter pain medication taken before or soon after an injection and/or application of a warm compress or heating pad to the injection site for 15-20 minutes following the injection.
- Given the delay many patients will experience obtaining CAB-LA, clinicians should consider a rapid initiation of oral PrEP for any patient requesting such protection – to delay PrEP initiation in these circumstances exposes patients to ongoing risk of HIV acquisition.
- If patients or providers have concerns about tolerability of CAB-LA, an oral lead-in with oral cabotegravir is a reasonable option.
- Clinically, a lead in of oral cabotegravir is not needed to achieve adequate blood levels of CAB-LA upon initiation of injections.
In HIV-1 treatment clinical trials, data demonstrated that an oral lead-in is not needed to ensure adequate plasma cabotegravir exposure upon initiation of injections and that the safety and efficacy results of cabotegravir extended-release injectable suspension plus rilpivirine extended-release injectable suspension were similar when administered with and without an oral lead-in. There were no discontinuations of oral cabotegravir among almost 4,000 participants in HPTN 083/084 due to drug-related hypersensitivity, supporting the optional status of the oral lead-in on the package inset. It may be a reasonable option for patients and providers with concerns about tolerability; but patient and provider concern about the adherence burden of a daily oral pill might also be considered.
- Oral cabotegravir tablets for this purpose – that is, explicitly as an HIV prevention strategy– is technically “off-label” according to the FDA package insert.
- FDA approved regimens to date for oral PrEP include generic TDF-FTC, or brand Truvada (TDF-FTC ) or Descovy (TAF-FTC)
Oral cabotegravir tablets were approved for assessing tolerance to this drug compound and for short-term PrEP in the setting of planned missed doses (see below).
- To cover known delays or gaps in CAB-LA of up to two months, when the patient plans to miss an injection visit but wishes to continue CAB-LA as soon as interrupting factors are resolved.
See Appendix #3 ”Continuing CAB-LA following Planned or Unplanned Missed Injections” for recommendations
- The decision to administer a shorter course of oral cabotegravir lead-in (<28 days) to assess medication tolerability is up to the provider, in consultation with the patient.
The oral cabotegravir lead-in is optional and in the HPTN studies, it was administered for 5 weeks.
It would be reasonable to restart daily oral PrEP (TAF-FTC or TDF-FTC) 7 days prior to the date on which the next CAB-LA injection would have been administered, were the patient to have continued injectable PrEP.
An alternative form of PrEP should be initiated within 2 months of the final CAB-LA injection. Ideally, 7 days prior to the date on which the next CAB-LA injection would have been administered.
- Available evidence suggests that seven days after the first CAB-LA injection would be the appropriate time to stop oral TDF-FTC or TAF-FTC.
Based on population PK modeling, 95% of the population would have CAB LA levels consistent with protection within 7 days following the initial injection. In the ongoing open label extensions, participants are being switched without overlap; data on switch from oral TDF/FTC to CAB LA are being collected.
- There is a theoretical risk that if a CAB-LA patient is lost to follow-up, and experiences a very gradual waning of CAB-LA drug levels over many months (up to a year perhaps), not only is the patient at risk of acquiring HIV, but were the patient to contract HIV infection in this time period, the exposure to subtherapeutic blood levels of CAB-LA could induce drug resistance in the acquired virus – resistance to either cabotegravir, or perhaps the entire integrase inhibitor class of antiretrovirals more broadly.
Fortunately, in study results available to date, HIV seroconversions have not been documented. However, numbers observed to date have been relatively small, so caution is recommended in drawing definitive conclusions especially in patient communications.
- According to available data, there are no gender differences in clinical or practical concerns in the use of CAB-LA for HIV PrEP. Therefore, neither counseling messages nor prescribing practices need to be varied based on the gender of the patient/client, or whether the patient/client is at risk of HIV infection due to vaginal versus anal sex/exposure, etc.
Of note, aside from plasma levels of CAB-LA, there was no sampling of anatomic tissue compartments in HPTN 083 or 084 to predict with certainty what drug levels would be in those compartments. However, there were no observed differences between participants of different genders in the studies.
- Not according to available data.
According to available data, there are no differences in clinical or practical concerns in the use of CAB-LA for HIV PrEP for persons on hormone therapy. Transgender women were included in HPTN 083 The cabotegravir-LA label does not call for any dose adjustments for persons on GAHT.
For reasons including patient preference, presence of gluteal implants, and management of injection site reactions (ISRs), clinicians have considered the appropriateness of administering CAB-LA at alternative anatomic sites. Data on administration of CAB-LA for PrEP in an alternative muscle group are not yet available but early pharmacokinetic data are promising. In a phase I treatment study, a single intramuscular dose of 600mg of cabotegravir and 900mg of rilpivirine administered in the in the lateral thigh achieved levels comparable to gluteal injections though a higher rate of ISRs was observed.
Evidence suggested that oral tenofovir-based PrEP is effective in reducing risk of HIV acquisition in people who inject drugs (PWID) by an estimated 74%. (CDC) No data are yet available to support the use of injectable CAB-LA in those who inject drugs, despite the observation that an injectable agent might be preferred or more practical for use among those for whom daily pill adherence is challenging or who are unable to store oral medication. A small qualitative study found that injectable PrEP was acceptable among PWID. (Biello et al.) For PWID who also are at risk of HIV acquisition via sexual activity, oral or injectable PrEP are indicated for use.
- No, there are no data to support varying dosage amount or frequency based on weight or BMI.
- A longer needle length should be considered for persons who weigh >30 kg to ensure the medication reaches the gluteus muscle.
For additional clinical support, contact the National Clinician Consultation Center PrEP line:
(855) 448-7737 or (855) HIV-PrEP, Monday – Friday, 9 am – 8 pm ET.